From the blog "Skyrim Notes to Myself"
Like many other things I've tackled in Skyrim, dealing with Body Slots requires the use of tools over and above what the typical mod user needs. Specifically, you need:
TES5Edit
https://www.nexusmods.com/skyrim/mods/25859
NifSkope
http://niftools.sourceforge.net/wiki/NifSkope
and optionally but highly recommended:
Body Slots MCM
https://www.nexusmods.com/skyrim/mods/64976
The Body Slots MCM mod is loa